John Kutzbach's career contributions to climate science are broad and deep. After a distinguished early career in atmospheric sciences, he shifted into paleoclimate during the 1970s. His subsequent research used general circulation models to explore several problems, including insolation and icesheet forcing of regional climates during the last deglaciation and in the late Holocene, the megamonsoon climates on the supercontinent Pangaea, and the climatic impacts of uplift of Tibet. These and other studies are characterized by an impressive economy of design, clarity of interpretation, and depth of insight into the operation of the climate system. Together, this body of work forms a large part of the framework of our current understanding of past climates.